1. Field of Invention
This invention relates to dispensers for viscous fluids and more particularly to a dispensing pen which is operative for effectively and accurately dispensing controlled amounts of a viscous fluid.
2. Description of Prior Art
Currently, the most common type of dispenser for viscous fluids is the plastic squeeze bottle. While they are economical to produce, they are limited in the length of continuous line they can extrude before they must be allowed to return to their original shape. This introduces air bubbles into the fluid which can be extruded in subsequent use. Start and stop blobs and occasional bubbles are common problems. Also, many people with arthritis, carpal tunnel syndrome, or other wrist or hand problems find it difficult and tiresome to exert the constant pressure necessary to extrude a nice even line.
Also on the market are miniature caulk guns. These use medical type syringes for barrels and a ratchet trigger assembly to advance a piston for extruding a fluid. From the hand's position on the trigger these devices lack precise control over the tip. Like the squeeze bottle they are limited in the length of continuous line they can produce. Also, constant pressure must be maintained to produce an even line and hand fatigue is again a problem.
Another approach, used mainly in industry, is a dispensing pen that has a separate reservoir containing the fluid which is pressurized with air. The fluid is forced through a tube to a hand-held instrument containing a control valve. While working effectively, this dispenser requires a regulated air supply and is difficult to clean between fluid changes. To accomplish cleaning, the valve body must be disassembled and the reservoir and supply tube must be emptied and flushed.
A fourth, and the most expensive approach, is another air powered device. Basically, this is a syringe for holding the fluid fitted with a cap and an air line. This air line is connected to a control box hooked to a regulated air supply. The control box contains a venturi apparatus, so by means of a foot switch the operator can pressurize the syringe and extrude fluid through the tip, or release the switch and create a partial vacuum in the syringe and stop all flow of material. These units work well, but are expensive by themselves, and in addition require a regulated air supply. This amount of equipment can be cumbersome as well if weight or space is a consideration.